Cryogenic tank and tank liner with curved flanges

ABSTRACT

A tank liner sheet with an integral, curved, floor portion of diminishing width and relatively high, curved, side-edge flanges is made by a process which comprises holding the metal sheet substantially stationary on a fixed platform, while pulling a series of roller benders, together with an edge-trimming device, along on an arcuate path adjacent to the sheet being flanged. Special clamp means are used to minimize distortion in sheet position caused by stress on the sheet being processed.

United States Patent [1 1 [111 3,874,545

Struss Apr. 1, 1975 [54] CRYOGENIC TANK AND TANK LINER 1,286,628 12/1918Herrman et a1. 220/5 R WITH CURVED FLANGES 1,287,019 12/1918 Herrman etal.... 220/5 R 1,358,203 11/1920 Herrman et a1.... 220/5 R X [75]Inventor: Leigh A. Struss, Nashua, NH. 1,417,617 5/1922 McNeil 220/5 R XAssigneez Martin Welding Inc. Lowe, Mass 1,428,337 9/1922 McNeil 220/5 RX 1 Flledi p 12, 1973 Primary Examiner-William 1. Price 21 A L N 350 349Assistant Examiner-Steven M. Pollard 1 pp 0 Attorney, Agent, orFirmPearson & Pearson Related US. Application Data [62] 3Di7vs5io2nl(l)fSer. No. 226,640, Feb. 25, 1972, Pat. No. 57 S C I A tank liner sheetwith an integral, curved, floor por- 52 us. Cl. 220/5 A, 220/1 B,220/83, tion of diminihing Width and relatively high, curved 220/63 Rside-edge flanges is made by a process which com- 51 Int. Cl B65d 7/02prises holding the metal sheet substantially stationary 58 Field ofSearch 220/5 A, 5 R, 1 B, 63 R, on fixed Platform, While p g a series ofroller 20/78 83 75 7 77; 52/245 benders, together with an edge-trimmingdevice, along on an arcuate path adjacent to the sheet being [56]References Cited flanged. Special clamp means are used to minimizeUNITED STATES PATENTS distortion in sheet position caused by stress onthe h tb d. 362,107 5/1887 Penfield 220/5 R s ee emg processe 1.2585383/1918 Dar1ey,.1r. 220/5 R 5 Claims, 9 Drawing Figures PATENTED APR 1I975 snmlq g Mil Fig.2

CRYOGENIC TANK AND TANK LINER WITH CURVED FLANGES This application is adivisional application of Ser. No. 226,640 filed 2/25/72, now US. Pat.No. 3,765,211.

BACKGROUND OF THE INVENTION It has long been a problem to form sizeableflanges on elongate metallic sheets. This has been especially so whenthe flange followed an especially complex or compound curve" type ofpath. Usually such flanges have been shaped by manual operations whilethey are held in a metal brake, an exceedingly expensive practree.

In US. Pat. No. 3,462,989, Fischer disclosed an apparatus for flangingsheet material, but Fischer was directing his efforts to forming simpleflanges and does not attempt to solve the primary problem faced byapplicants. i.e., that of forming a flange with a base line whichdefines a compound curve on the sheet. Another drawback to the apparatusdefined by Fischer was the fact that a large amount of floor space isrequired for the operation of his apparatus.

Nowhere in the prior art has there been any suggestion of apparatusadapted to form complex flange configurations. Yet such apparatus wouldhave a high utility, especially if it minimized the amount of residualstrain left in the metal being worked, thereby providing not only animproved process but more reliable products adopted for utility inconstructing such structures as, say, cryogenic tanks and the like.

SUMMARY OF THE INVENTION Therefore it is a principal object of theinvention to provide an improved process and improved apparatus forforming flanged edges on metal sheet material, especially for formingsheets having compound curves along the flange line.

It is a particular object of the invention to provide apparatus forflanging the edges of sheet material which apparatus permits theoperation to be carried out in minimal floor space.

A further object of the invention is to provide a means for formingflanges along sheets of varying width. and especially whereon theflanged area must curve with respect to the center line of an elongatesheet being processed.

Another object of the invention is to provide flanging apparatus such asdescribed above which imparts a minimal amount of stress to the metalbeing worked, thereby making it dependable for use in construction ofstructures requiring very high structural reliability and integrity.

Another object of the invention is to provide relatively simpleapparatus for making complex flanges on elongate sheet.

Still another object of the invention is to provide flanging apparatuswhich incorporates an integral and improved means for accuratelytrimming the edge of the material being flanged. v

A further object of the invention is to provide apparatus of the typedescribed in the foregoing object whereby the sheet to be flanged isheld in adaptive clamp means to minimize the effect of stresses exertedon the sheet during the flanging operation.

Other objects of the invention will be obvious to those skilled in theart on reading the instant invention.

In the practice of the invention, a thin elongate sheet is held on astationary platform while a travelling rollerbender assembly, togetherwith an edge trimmer, traverse one long edge of the sheet, eachsequential rollerbending device in the assembly causing the edge of thesheet to be bent into a more upright position. Sheets to be so processedwill usually be trimmed roughly beforehand; however, fine trimming isadvantageously accomplished by use of an edge-trimming device mountedfor movement with the roller-benders along the stationary platform.

The sheet is firmly clamped to the platform by means of convenientfastening devices at one end; at the other end, however, it has beenfound desirable to provide a pivoted pressure-clamp means. Mostadvantageously this clamp comprises a number of pivot points so that itmay be self-adjusting to various stress vectors exerted thereon duringthe processing operation, and thereby insure that such stresses will notcause any undesirable warping of the sheet on the platform. It has beenfound that such bending stresses are minimized and most easilyaccommodated, when this clamp is used while a single side of the sheetis being flanged at a given time.

The platform has two tracks mounted along the sides thereof along whichthe roller-bender assembly with its rolling and trimming devices arecarried during the processing operation. These tracks comprise arcuatesections positioned wherever necessary to achieve the appropriate curvefor the flange. Most advantageously the curved sections are placedproximate to the fixed end of the sheet. In the typical case, this willbe convenient because the curves desired in the sheet will be at oneend, corresponding to a position in a structure, such as a cryogenictank, where there is a change in diameter or radii at one end thereof,e.g., where the bottom of the tank curves inwardly to a disked-shapedbottom or top.

In general, the apparatus and process of the invention have been foundto be entirely satisfactory for processing stationary elongate sheetswhile accommodating the strains and stresses encountered in theoperation and minimizing the factory floor space required for theoperation.

A typical sheet to be flanged in accordance with the invention will be a304-type stainless steel sheet having an average thickness of about 0.02inches. Such a material is elected primarily for its utility in makingcryogenic tanks, i.e., for its ductility tensile strength, and corrosionresistance. However, as will be obvious to those skilled in the art, theprocess of the invention can be adapted for processing a wide range ofmetallic sheet materials. In making cylindrical tanks, it is common thatthe sheet be somewhat rounded rather than absolutely flat. The sheetsprocessed by the apparatus are often arcuate in shape, say from 3 to 6in magnitude of are when received in section normal to the longdimension thereof.

ILLUSTRATIVE EMBODIMENT OF THE INVENTION In this application andaccompanying drawings are shown and described a preferred embodiment ofthe invention. Various alternatives and modifications thereof aresuggested, but it is to be understood that these are not intended to beexhaustive and that other changes and modifications can bemade withinthe scope of the invention. The suggestions herein are selected andincluded for purposes of illustration in order that others skilled inthe art will more fully understand the invention and the principlesthereof and will be able to modify it and embody it in a variety offorms, each as may be best suited in the condition of a particular case.

IN THE DRAWINGS FIG. 1 is a plan view of the apparatus of the invention,showing two tracks mounted along the sheet holding platform and apivoted clamping device at one end thereof.

FIG. 1A shows one sheet clamp means.

FIG. 2 shows, in elevation, a roller-bender assembly mounted on a trackadjacent to the platform.

FIG. 3 shows, in perspective, a sequential rolling operation.

FIG. 4 is an elevation of a sheet trimmer used in the process of theinvention.

FIG. 5 illustrates means for moving rails in relation to the platform,the roller-benders and the sheet being bent.

FIG. 6 is a perspective view illustrating utility of sheets formedaccording to the invention in the construction of cryogenic tanks.

FIG. 7 shows means for holding a sheet being processed.

FIG. 8 shows a perspective view of a flanged sheet formed according tothe invention, including the integral lower floor portion of diminishingwidth and uncrimped, upstanding side-edge flanges.

Referring to FIG. 1, it is seen that a sheet-processing assemblycomprises a sheet platform 17, two carrier rails 19 mounted adjacenteach side of platform 17, and clamp means 29 and 23 mounted at each endof platform 17. At one end of each rail 19 is an arcuate rail section25. The sheet to be processed on assembly 15 is not shown in FIG. 1. Asseen in FIG. 1, rails 19 extend beyond platform 17 at both ends thereofto accommodate the required travel of processing equipment, describedbelow, which is carried on the rail 19.

Clamp means 23, mounted adjacent arcuate rail sections 25 is illustratedin FIG. 1A. It comprises upper and lower clamp bars 27 and 29. Theseclamp bars are tightened about a metal sheet 31 by bolt-tightening means33. The processing apparatus carried on the rails 19, and best seen inFIGS. 2 through 4, include roller-bending modules 35 and edge trimmer37. Roller bending modules 35, as illustrated in FIG. 2, include a lowerroller member 39 comprising a cylindrical section 41 and a truncatedconical section 43. The circumference of the cylindrical section 41 istangentially positioned with respect to a sheet 31 being held onplatform 17. The sheet 31 is bent upwardly by being forced againstconical section 43, and the angle with which section 43 is positionedwith respect to the circumference of section 41 is a measure of theamount of bend applied to the sheet by the module 35 to form a flange38. Bending pressure is applied by engagement of lower member 39 with anupper cylinder 45 mounted to engage cylindrical section 41 as theassembly is pulled along rail 19. The clearance between rolls 45 and 41is preferably equal to the thickness of the sheet.

As seen in FIG. 1, a plurality of roller-bending modules 35 are mountedon a rail 19 and pulled along at, say, feet per minute by a winch 47mounted on extension 48 of a rail 19. Each sequential roller-bendingmodule 35 imparts a somewhat more severe bend to the edge of the sheetbeing formed. While three modules 35 are shown, preferably six are usedin practice.

FIG. 4 also shows a metal trimming device 37 advantageously mountedbetween two roller-bending modules 35. Although the sheet isrough-trimmed before being placed into the apparatus, it has been foundto be more desirable to have the finish trimming done between tworoller-bending modules. There are a number of advantages to this featurein that the excess metal to be trimmed is present and can be engaged bythe first module 35 to help in performing the bending action, but istrimmed off before it gets to a following module where it couldinterfere with a proper bending'to the increased angular displacement.

FIG. 4 shows details of the trimmer assembly 37. The device comprisestwo shafts 53 journalled in bearings 55 for rotation. Each shaft 53carries a roller 57. Rollers 57 are spaced with a roll cutter member 59on the other shaft to admit, snugly fitted, the edge of metal sheet 31.The frictional engagement of the sheet between rollers 57 and adjacentroll cutter 59 causes the rotation of shafts 53 and of roll cutters 59carried thereon. Opposing roll cutters are spaced to assure cuttingaction. The trimmer 37 is mounted in a housing 61 riding on track 19 andis interconnected with brackets (such as those shown at 63) to modules35 and, consequently, integrated into a roller-bender assembly which ispulled along the length of the track on modulesupporting rollers by theaction of winch 47.

In FIG. 1, it will be observed that there are a number of rows ofreceptors 67 spaced therealong. These are to receive hold-down clamps 69which may be used for holding down that side of the sheet 31 which isnot being processed. Use of such clamps are especially useful whensheets 31 vary markedly in width. Such a clamp 69 is seen in FIG. 7 andcomprise a pin 71 inserted in receptor 67. Pin 71 restrains sheet 31laterally while a hold-down dog 73 contacts the upper side of sheet 31and holds it down against platform 17. Receptors 69 are advantageouslyconnected to the support bracing 74 which supports platform 17.

As seen in FIGS. 2 and 5, minor lateral adjustments in positioning therails are carried out by adjusting the lateral position of rails 19.These rails are supported on leg support brackets 75 which are slidinglysupported on cross beams 83 (See FIG. 1). Positioning assemblers 77comprise a stop lever 79 and a threaded positioning bolt 81. Assemblies77 are so placed along rails 19 that the stop lever 79 can be positionedfor engagement with the adjacent end of a lateral brace member, e.g., anl-beam 83 mounted on platform support legs 85.

FIG. 6 is a schematic diagram defining the type of tank which is madepossible by use of sheets formed according to the invention. It is seenthat the tank comprises a large number of flanged metal sheets 31 whichform the sidewall 87 of tank 89. These sheets are not only bent radiallyto form part of the circumference of tank 89, but they are also bentinwardly to form a major part of the transition curve 91 to the bottomring 93. Plates 31 are welded to this bottom ring.

Ring 93 is, in turn, welded to radially-arranged bottom plates 95 andthese are, in turn, connected to a center ring 97 Flanges 38, formedaccording to the process of the invention, are so placed that they arebent inwardly.

When the interior edges of these flanges are welded together, the wallsof adjacent flanges form a suitable expansion joint or diaphragm 101.

A consideration of the tank shown in FIG. 6 shows that a complex3-dimensional curve is required for the sheet 31. Not only must it havean upper wall portion to curve around the major circumference of thetank, but it must have an integral. lower, floor portion 108 to curveinwardly at the bottom of the tank and, at the same position, it mustconform to the diminishing width of the lower, flat surface, floorportion of the sheet. That manufacture of such a sheet is possible is,perhaps, within the ken of those skilled in the metal working art.However, applicants efficient method of manufacturing such asheet whileminimizing mechanical working and residual stresses in the metal isbelieved to be a significant contribution to the art.

FIG. 8 illustrates a sheet 31 formed according to the invention. Upperflat surface, wall portion 103 forms part of the inner surface of tank89. Flanges 38 bend upwardly and inwardly according to compound curve105, along baseline 107 of the flange and are uncrimped as at 109 and110 in the integral lower floor portion 108.

The upper wall portion 103 of sheet 31 is substantially flat in apredetermined plane to form the cylindrical side wall of the tank.Unlike a flanged stave of a conventional small metal barrel, wherein thelower end of the flanged stave is curved outwardly and free of flanges,the thin, approximately 30 feet long sheet body 31, has an integrallower end bent inwardly in a transition curve of gradually decreasingdiameter as shown in FIG. 8. Thus the integral lower floor portion 108terminates at a lower edge portion which is substantially horizontal tomerge with a generally horizontal bottom ring 93. Also unlike aconventional, flanged, metal, barrel stave the upstanding flanges 38,are continuous from top to bottom of the body 31 including thetransition curved portion 91 and terminal floor portion 103.

It is to he understood that the following claims are intended to coverall of the generic and specific features of the invention hereindescribed and all statements of the scope of the invention which mightbe said to fall therebetween.

What is claimed is:

1. An elongated, relatively thin metal sheet adapted to form a linersection of an expansible wall and floor of a cryogenic tank, said sheetcomprising:

an elongated body having an upper wall portion and an integral lowerfloor portion with an upstanding flange along each opposite longitudinaledge thereof, said flange being bent along a compound curved base lineprogressively and evenly with a roll bent appearance free of unwantedcrimps and wrinkles,

said lower floor portion being bent inwardly out of the plane of saidupper wall portion in a transition curve to a terminal lower edgeportion substantially in a horizontal plane for merging with the floorof said tank,

said body being at least 30 feet long, 2 feet wide and of stainlesssteel and each said flange extending continuously the full length ofboth said longitudinal side edges, of said upper wall portion and saidlower floor portion to a height of at least 2 inches, while being freeof crimps, fractures or pleats.

2. A cryogenic tank formed of sheets as defined in claim 1, each saidsheet having said continuous, full length edge flanges and having eachsaid edge flange continuously welded to an adjacent similar edge flangeof a juxtaposed said sheet including the flanges of said lower floorportions to permit expansion and contraction of the resulting expansionjoint, or diaphram, without gas leakage.

3. An elongated sheet as specified in claim 1 wherein:

said sheet body diminishes in width from the said upper wall portion tothe terminal edge portion of the said lower floor portion thereof.

4. An elongated sheet as specified in claim 1 wherein:

said lower floor portion is bent inwardly out of the plane of said upperwall portion in a transition curve of changing diameter.

5. An elongated sheet as specified in claim 1 wherein:

said transition curve progressively diminishes in diameter toward thelower edge portion of said lower floor portion.

1. An elongated, relatively thin metal sheet adapted to form a linersection of an expansible wall and floor of a cryogenic tank, said sheetcomprising: an elongated body having an upper wall portion and anintegral lower floor portion with an upstanding flange along eachopposite longitudinal edge thereof, said flange being bent along acompound curved base line progressively and evenly with a roll bentappearance free of unwanted crimps and wrinkles, said lower floorportion being bent inwardly out of the plane of said upper wall portionin a transition curve to a terminal lower edge portion substantially ina horizontal plane for merging with the floor of said tank, said bodybeing at least 30 feet long, 2 feet wide and of stainless steel and eachsaid flange extending continuously the full length of both saidlongitudinal side edges, of said upper wall portion and said lower floorportion to a height of at least 2 inches, while being free of crimps,fractures or pleats.
 2. A cryogenic tank formed of sheets as defined inclaim 1, each said sheet having said continuous, full length edgeflanges and having each said edge flange continuously welded to anadjacent similar edge flange of a juxtaposed said sheet including theflanges of said lower floor portions to permit expansion and contractionof the resulting expansion joint, or diaphram, without gas leakage. 3.An elongated sheet as specified in claim 1 wherein: said sheet bodydiminishes in width from the said upper wall portion to the terminaledge portion of the said lower floor portion thereof.
 4. An elongatedsheet as specified in claim 1 wherein: said lower floor portion is bentinwardly out of the plane of said upper wall portion in a transitioncurve of changing diameter.
 5. An elongated sheet as specified in claim1 wherein: said transition curve progressively diminishes in diametertoward the lower edge portion of said lower floor portion.